show and tell, part 2

Onward to the second and third rows, where we’ll actually get to stuff that directly makes noises!  And has orange knobs!

But first:  on the left we see a Pittsburgh Modular Lifeforms Dynamic Impulse Filter.  This is a modern non-vactrol LPG with a classic design, with a mode switch that lets you select whether it’s going to act as a VCA, an LPG, or a lowpass filter.  Its response to triggers is not to my liking, but it works well controlled manually or via CV.  It has a uniquely woody tone, and controls that make it handy in any mode.  4/5.

Filters, particularly VCFs (voltage-controlled filters) are important building blocks in synthesizers.  (Subtractive synthesis, the most common technique, is performed by pairing a harmonically rich simple oscillator with a filter.)

Filters reduce frequencies in part of the spectrum, while optionally emphasizing it in others (called resonance).

A lowpass filter allows lower frequencies to pass through while quieting higher ones; a highpass filter does the opposite.  A bandpass filter allows only a narrow band of frequencies to pass through freely, while a notch filter reduces only a narrow band of frequencies.  A multimode filter typically will either switch between these or provide all of them simultaneously.

Different circuit designs have widely different characteristics in terms of slope, resonance, stability, phase characteristics and so on.  Many designs will self-oscillate when the resonance is high enough, producing very pure tones even without input. 

 Equalizers (EQ) and tone controls are an especially gentle type of gentle filter.

Next is the Doepfer A-196 PLL (phase-locked loop).  This is a strange beast!  Given incoming signal (audio rate or slower), it attempts to match the frequency and create its own set of pulses.  It does this by constantly measuring whether it’s ahead or behind, and feeding back a signal to itself to make adjustments… but depending on settings, the material it’s tracking, and how much you intentionally confuse it, it can be joyfully terrible at its job.  The open nature of this module lets you do all kinds of bizarre tricks with it.  One of my favorites is patching in a different oscillator instead of its own — perhaps one that’s trying to modulate itself and therefore can’t properly track pitch without extra help.  4/5 (it’s pretty situational, and there’s sometimes a razor-thin margin of error between good tracking and garbage).

The leftmost orange-knobbed module is the Hertz Donut mk2 by The Harvestman (now called Industrial Music Electronics).  It’s a proudly digital take on the Buchla 259-style complex oscillator.  It’s not a very clean sound to start with, and includes phase feedback as an option on its modulation bus, a harsh “discontinuity” control rather than a typical waveshaper, as well as an XOR output which is a rough sort of ring modulation.  But FM with it is super-easy and the thing really can be beautiful, especially through an LPG.  4.9/5!  (If it remembered its state when powered down that’d be perfect.)

An oscillator generates a signal that repeatedly fluctuates between positive and negative voltages.  This is the most important building block in any synthesizer.  (Cue people arguing that the filter is more important, but I say, not without something to filter!)

A VCO is a voltage-controlled oscillator, which is the kind most relevant to us in modular synths.  VCOs use the 1V/octave standard for frequency control and typically work at audio rates (20 to 20,000 cycles per second, or Hertz (Hz)) just like sound waves.

If it’s slower than that, it’s an LFO — low frequency oscillator — and rather than making sound, it will control or modulate something else.  Some LFOs can synchronize to a clock signal to stay on rhythm; many VCOs also can synchronize, which can have interesting effects on the sound.  (It’s rare for VCOs to be much faster than audio rate, but there are specialized uses for it.)

The shape (or waveform) produced by the oscillator determines the sound (or timbre, which annoyingly is pronounced “tam-ber”).  There are a few common ones in synthesis because they’re easy for analog circuits or very simple code to produce — triangle, sawtooth, pulse/square, and sine — but some oscillators can create extremely complex shapes.

Complex oscillator is a term for a specific configuration as used in the Buchla 259 and many imitators.  It consists of a pair of oscillators that can track together and modulate each other through FM and in other ways, frequently using a “mod bus” to assign and control the amounts.  The “primary” oscillator also includes a waveshaper or wavefolder which further increases the harmonic complexity.  This is the quintessential West Coast design, rarely seen outside of modular synthesizers.  (Some people use “complex oscillator” in a more generic adjectival sense, but this is discouraged.)

Generally, analog oscillators are prized for a sort of mythic “warmth” and other subtle qualities, while digital oscillators are much more diverse in terms of shapes they can generate as well as potentially more precise (or imprecise in specific ways).  A common type of digital oscillator is the wavetable, which keeps shapes in memory and can smoothly change between them.  Other digital oscillators are based on mathematical models and algorithms computed in real time.

FM, frequency modulation, is a synthesis method where the output of one oscillator modifies the frequency of another oscillator.  Slow FM is just vibrato, but at audio rates the result is instead a change in timbre, which can be brassy or bell-like or incredibly noisy depending on the frequency ratio between the two oscillators.  Many non-modular synths like the famous Yamaha DX7 actually use phase modulation (PM) which is similar but simpler in some ways.  In the modular world, one deals with exponential vs. linear FM, thru-zero and other complexities having mostly to do with keeping things in tune while being able to shift the timbre at will.

There’s also AM or amplitude modulation, which is simply controlling a VCA with a second oscillator harmonically related to the first but has somewhat similar timbral effects; RM or ring modulation, and filter FM which modulates the cutoff frequency of a filter at audio rates, producing a combination of amplitude and phase modulation.

(An aside about my aside:  some people love to “debate” analog vs. digital audio.  This is less common among modular synth types, probably because we know it’s like arguing whether a wrench is better than a screwdriver.  If you use the most practical and appropriate technology for the function at hand, you’re probably going to have both.)

The next orange knobbo is The Harvestman Kermit, after Kermit Washington, the One Punch Man of basketball.  It was designed as a dual LFO based on a small wavetable, but it will also run at VCO rates, where it’s very noisy and fizzy and unstable in a beautifully disastrous way.  Something about it makes it especially well suited to amplitude modulation.  It would benefit from fine-tuning knobs, normal-sized knobs for the modulation inputs, and remembering button states on shutdown.  The clock/pitch following mode is a sloppy mess.  But the sound is unbeatable, and it works very nicely for LFO purposes.  4/5.

Then we have The Harvestman Tyme Sefari, named for a time travel company in a Ray Bradbury story.  It’s a lo-fi digital audio buffer that can capture and play back audio — a very flexible sampler or a delay/echo depending on how you configure it.  Like Chronoblob, it has an open feedback loop that adds flexibility.  But unlike Chronoblob, the sound just can’t avoid being grungy and that doesn’t always suit.  It’s also pretty large, especially with its expander module.  There’s a firmware update supposed to be coming soon which should make it less glitchy, and I’m pretty much waiting to see what I think of that before letting it go for something else.  3.5/5.

To its right is its expansion module, A Sound Of Thunder (which is the title of that Bradbury tale).  This adds a second channel to the TS which can be used for stereo or other nefarious purposes.  There’s no mix control though.  It also adds some marginally useful options to make the sound even worse or to shift the pitch.  It’s overly large for what it does.  2.5/5.

Getting back to white knobs again, we have the Antimatter Audio Crossfold.  This is a nice wavefolder with two inputs, which lets you crossfade between the two, control the folding amount two different ways, and fade between the original (or mixed) and folded signals.  This combination of features gives it some great sonic versatility.  5/5.

Here comes Bastl Cinnamon, a multimode filter.  It’s pretty straightforward and sounds good, with some switches to make it rougher.  I won it in a charity auction and it was supposed to have been the aluminum panel version, not wood — which is weirdly thick and doesn’t fit well, and makes the text labels hard to read.  Still 4/5.

Last are a couple of passive infrastucture bits.  The Doepfer A-180-9 Multicore lets me make 14 connections between this rack and the case on the other side of my desk through a pair of Cat-6 network cables and very compact panels.  (I am in the habit of keeping two lines to my audio interface, which on the other side are stereo outputs of one of my FX pedals.)  Unfortunately I still had to run a separate ground wire between the cases to eliminate hum.  If the two network jacks were both at either the top or bottom — and better yet, if they had a rear option — it’d be a little less unwieldy.  3.5/5.

The last tiny module with a row of nothing but jacks is a Bastl Multiple.  It passively connects all 9 jacks together, and you can configure it by snipping wires on the back. I divided this one into (2, 2, 2, 3) just to have a handy way to patch into 3 inputs and an output on the back of my audio interface.  Cheap and useful, 5/5.

The bottom row of the rack has just 5 modules, but the first one’s a doozy.  It’s a beta test version of the Synthesis Technology E370 Quad Morphing VCO.  It is the absolute monarch of wavetables, with four independent or coordinated VCOs.  Borderline overkill.

My main gripe about it is that dynamic linear FM is quite tricky to set up, compared to the ease of the Hertz Donut.  I believe it could be solved with a software tweak (a menu option for a DC blocking filter on the FM input while in linear modes) but can’t convince the DSP guy to try it, so it is what it is.  However, all the other audio-rate modulation you can do to the thing is fantastic — the internal 2-Op FM model, exponential FM, PM, AM, wavetable morphing, wavefolding — and you can create FM wavetables in the first place.  And the cloud mode is stupefyingly good.  So it’s a 5/5 for sure.

The next module with a screen is Dave Jones O’Tool+.  It’s a dual-trace oscilloscope, voltmeter, frequency meter, tuner, spectrum analyzer, and metronome.  It’s invaluable for learning new modules, setting up tricky patches, solving problems and giving you answers that your ears don’t.  5/5.

A patch is a “program” of modules and connections.  It can refer to everything you’ve got set up at any given time or a functional subset; it can be a general term (a bass patch, a Karplus-Strong patch, a feedback patch) or refer to exact settings.  The term is sometimes used outside the modular realm it’s also used to refer to a synth program or a configuration of gear.  Some people diagram them or photograph them; I sometimes take general notes.

A patch programmable module is one that takes on different behaviors depending on what’s patched into it — like the function generators I mentioned in the last post which can generate envelopes or LFOs, delay a gate signal, filter audio, smooth a stepped signal, and so on.  Multifunction modules, on the other hand, require changing between different mode to determine the behavior.  Of course, there are modules blur that line.

The plain-looking module with the eight knobs is Epoch Modular’s Twinpeak filter.  This has two inputs that can be mixed, and a knob to fade between a single lowpass filter mode and a dual bandpass.  At the highest resonance settings it doesn’t continuously self-oscillate, but a trigger into the input will make it ring in a lovely percussive way for a second or two.  I am not a big filter connoisseur since I lean more toward non-subtractive synthesis, but this one has proven itself to be pretty cool.  4/5 (a mix CV input would have been nice).

Frap Tools 321 is a three-channel offset and attenuverter, with a pair of mix outputs (one mixes everything, the other mixes only the channels where you haven’t patched the outputs).  Very useful for getting signals to the appropriate levels.  I’m not in love with the tiny black switches on the black panel with tinier labels, but it does the job. 3.5/5.

Finally there’s the S********k S***r P***r G***n.  It’s a power supply module.  Some time after I bought it, the owner of the company revealed himself as a misogynist alt-right toolbag and proud trust fund baby who, he says, doesn’t need any of us.  So I covered his logo with sparkly star stickers and never did business with him again.  The power supply works okay.

More happily, behind the panels I’ve got a Genus Modu Low Impedance Bus Board (LIBB) helping to distribute that power and keep it clean.

And that’s my rack!  Part 3 will cover the top row of my TipTop Mantis case, which is full of fun things that need explanation. 😉

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